As miniaturization progresses, conventional silicon microelectronics will reach its limits. In particular, the development of ever smaller and densely arranged transistors, nowadays amounting to several hundred millions of transistors per chip, will be subject to fundamental physical problems and restrictions within the next ten years. When feature sizes drop below approximately 80 nm, the components are disruptively affected by quantum effects, and these effects dominate at dimensions below approximately 30 nm. The increase in integration density of components on a chip also leads to a dramatic increase in the waste heat.
Nanostructures, such as for example nanotubes, in particular carbon nanotubes, and nanorods, also known as nanowires, are known to be a possible successor technology to conventional semiconductor electronics.
By way of example, the paper by PJF Harris, “Carbon Nanotubes and Related Structures—New Materials for the Twenty-first Century,” Cambridge University Press, Cambridge, pp. 1-15, 111-155, 1999, which is incorporated herein by reference, provides an overview of carbon nanotube technology. A carbon nanotube is a single-wall or multiwall, tubular carbon compound. In the case of multiwall nanotubes, at least one inner nanotube is coaxially surrounded by an outer nanotube. Single-wall nanotubes typically have a diameter of one nanometer, while the length of a nanotube may amount to several hundred micrometers. The ends of a nanotube are often terminated with, in each case, half a fullerene molecule.
Field effect transistors are required for many integrated circuits used in silicon microelectronics. A carbon nanotube can be used to form a field effect transistor of this type, resulting in the formation of what is known as a CNT-FET (“carbon nanotube field effect transistor”).
As an alternative to nanotubes, in particular to carbon nanotubes, nanorods, also known as nanowires, are used as nanostructures for an integrated circuit.
One problem with integrated circuit components based on nanoelements according to the prior art is that the controlled formation and driving of nanoelement components of this type is difficult.
Furthermore, German Patent Application No. 42 35 152 C2, which is incorporated herein by reference, describes an array of free-standing silicon columns, which are used to form vertical field effect transistors, the individual silicon columns being surrounded by means of a gate oxide, and the gate oxide in turn being surrounded by the gate material polysilicon.
U.S. Patent Application Publication No. 2002/0117659 A1, which is incorporated herein by reference, discloses a chemical sensor, formed from a single nanotube, the periphery of which is covered with a silicon oxide, which is in turn surrounded by fine gate material that has been functionalized with a view to the desired chemical reaction that is to be detected. The nanotube is provided as a free nanotube without adjoining substrate, and only electrical connections provided as source region and drain region of the field effect transistor formed are illustrated at the respective longitudinal ends of the nanotube.
The paper by J. Maultzsch, et al., “Raman characterization of boron-doped multiwalled carbon nanotubes,” Applied Physics Letters, Vol. 81, No. 14, pp. 2647-2649, 2002, which is incorporated herein by reference, describes properties of boron-doped multiwall carbon nanotubes.